Contrec 515 FA01, Operation Manual

Page: 68 / 98

Communications
58 515 FA01 - 29 August 2021
Note: The instrument requires a cable with straight-through connections.
Do not use a null modem cable for RS-232 connection to a computer.
COM-2 RS-485 Port Option
The COM-2 RS-485 port enables communication with multiple devices.
Each device has a unique address so that the “master” device can
communicate with specific “slave” devices.
On RS-485 links, an external terminating resistor must be connected at the
furthest end of the cable. When multiple instruments are connected, they
should be “daisy chained” in a multidrop configuration as shown in Figure
19. Up to 32 units can be connected to the interface at a maximum distance
of 1200 metres.
Figure 19 RS-485 Connections
COM-2 Ethernet Port Option
An Ethernet module is an available option, in place of the RS-485 port, if
Modbus TCP/IP connection is required. In the programming
communication settings, COM-2 should be set to RTU (Modbus), 19200
Baud rate, even parity and 1 stop bit.
For further advice and example of Ethernet port usage and setup, refer to
Ethernet Port & Setup on page 82 in the Appendix.
Twisted Pair
Load
120 ohms
Gnd Gnd
Host
Computer
Comms
Gnd
+
-
+ -
+ -
Instrument Instrument
19 20 21
19 20 21